All livestock is subject to lameness but dairy animals and specifically dairy cows are particularly vulnerable, due in part to the weight they carry, but also to their accommodation. In many modern diary farms cows are confined all year round in confinement systems with concrete floors. Over time, this surface can damage the hoof leading to lameness. Even in dairy farms that are pasture based, the animals have to stand on concrete floors in the milking parlour at least twice a day. In addition, the floor of the milking parlour is often wet, which can encourage infection.
Lameness can lead to a reduction in feed intake, a reduction in milk production and weight loss. Thus lameness has a drastic effect on the performance of a dairy animal. Lameness is conventionally detected by a herdsman by observing the movement of the animal and will often only be picked up once it has become severe requiring immediate and often costly treatment. Once an animal becomes lame, it can take several months to recover. Lameness thus represents a significant cost for livestock breeders and farmers in terms of time, financial expenditure for veterinary services, medication and treatment, and also for loss in production.
It is thought that the early detection of lameness can mitigate these losses as early treatment may enable an animal to recover more rapidly. A number of automatic lameness detection systems are known, however, these require the animal to perform some kind of movement, sometimes under controlled conditions, which, in a farm environment is often not practical or cost effective. U.S. Pat. No. 6,699,207 proposes a diagnostic system for detecting lameness in dairy cattle which consists of a system of plates placed over load cells provided at floor level and over which the animals must walk. The system determines and analyses the animal's limb reaction forces, weight, bilateral symmetry of limb reaction forces and other factors as the animal passes over the plates and compares these with reference data obtained when a healthy animal passes over the plate. The drawback of this system is that reference data must be provided, preferably for each animal, requiring all animals to walk over the system when healthy at least once. The system of plates is also cumbersome and large requiring adequate floor space and considerable installation costs.
Further systems propose the attachment of sensors to the animal to detect abnormal movement. A problem with these systems is how to ensure that the sensors remain fixed on the animal in what may be an inherently dirty environment without reverting to invasive techniques that require costly veterinary or specialist intervention and may cause unnecessary distress to the animal. WO 2006/009959 describes a system for monitoring the condition and wellbeing of dairy animals that includes a monitor unit fixed to a collar, strap, transdermal patch or ingested bolus carried by the cow that includes a number of sensors, one of which is an accelerometer. Lameness is determined by analysing the signals from the accelerometer to detect an abnormal gait, which could indicate lameness. A fixed unit is provided which collects data from the monitoring unit wirelessly and analyses this. A problem with this system is the complexity of the signals that will be produced as any movement of the cow, including raising or lowering its head, will be registered by the accelerometer. Added to this is the difficulty in ensuring that the accelerometer does not move on the cow. Moreover, determining signals that indicate an abnormal gait and possible lameness is complex and prone to error, resulting in unreliable results. WO 2006/009959 proposes a similar system for monitoring the gait of a horse wherein patches consisting of piezoelectric film are attached to each hoof of the horse. The signals produced are analysed and compared to reference signals, which are collected from the same animal or a group of other animals previously. This system must be used in a controlled and clean environment as the location of the sensors on the hooves of the animal would otherwise put them at risk of damage.
There is thus a need to improve on the automatic early detection of lameness.